The invention relates to an anode for a direct current arc furnace.
EP 422 406 discloses an anode for a d.c. arc furnace, in which the area of the furnace which receives the melt is provided with an electrically conductive refractory lining and on whose outside is electrically conductively applied an annular or cylindrical conductor.
Apart from the conductor, which is preferably a copper ring, the anode comprises several layers made from materials with different characteristics. The layer in direct contact with the melt is formed from an electrically conductive, refractory material, such as e.g. carbon-magnesite in areas not coming into contact with the melt, the lining is made from graphite bricks, which have a much better conductivity than carbon-magnesite.
The entire layer structure and also that of the conductor surrounding the furnace are rotationally symmetrical, so that in the radial direction a relatively homogeneous electric flow field is built up. The resulting magnetic field keeps the arc in a central position.
With this anode construction for a d.c. arc furnace a uniform temperature distribution of the melting stock is ensured, unless magnetic fields located outside the furnace vessel and which an e.g. be caused by the provision of supply or leakage cables, disturb this symmetry and deflect the arc in an undesirable manner.
It is also not possible to heat more strongly in planned manner certain areas of the melt, such as is e.g. necessary in the case of bottom tapped furnaces. It is also not possible to influence in a desired manner the movement in the molten bath.
it is known from DE-OS 40 35 233 to compensate the arc deflection caused by magnetic fields located outside the furnace vessel by additional magnetic fields produced by current-carrying conductors located on the furnace bottom.
DE-OS 34 23 677 discloses a d.c. arc furnace, in which particular importance is attached to the symmetrical design of the bottom electrode serving as the anode. In this furnace the power supplies from the rectifier to the bottom electrode are arranged symmetrically. This arrangement was chosen in order to prevent any influence on the formation of the magnetic field, which would have a negative influence on its symmetry and therefore being about a deflection of the arc.
The solutions described in the two aforementioned publications suffer from important disadvantages, because they involve considerable electrical equipment expenditure.